Jingyuan Wen

Formulation of oil-in-water β-carotene microemulsions: Effect of oil type and fatty acid chain length

The impact of oil type and fatty acid chain length on the development of food-grade microemulsions for the entrapment of β-carotene was investigated. The microemulsion region of a ternary phase diagram containing short chain monoglycerides was larger than for di- and triglycerides when Tween 80 was used as surfactant. The cytotoxicity of microemulsions composed of a 30% monoglyceride oil, 20% Tween 80 and 50% aqueous buffer were evaluated using an in vitro cell culture model (human epithelial colorectal adenocarcinoma, Caco-2). The cytotoxicity test showed that the viability of Caco-2 cells against β-carotene microemulsions at concentrations of 0.03125% (v/v) was higher than 90%. This study suggests that short chain monoglycerides could be used with Tween 80 to prepare transparent β-carotene-encapsulated O/W microemulsions in the particle size range of 12-100 nm.

Antioxidant activity and bioaccessibility of size-different nanoemulsions for lycopene-enriched tomato extract

Lycopene nanoemulsions were prepared to protect the antioxidant activity and improve the bioaccessibility of lycopene-enriched tomato extract (containing 6% of lycopene) by an emulsification-evaporation method. Lycopene nanoemulsions, with droplet sizes between 100 and 200 nm, exhibited higher anti-radical efficiency and antioxidant activity, than did those smaller than 100 nm. Strong protectability of lycopene in droplets smaller than 100 nm was associated with relatively slower rates of DPPH and ABTS reactions. In vitro bioaccessibility values of lycopene-enriched tomato extract, lycopene nanoemulsions with droplets larger than 100 nm (approximately 150 nm on average), and lycopene nanoemulsions with droplets smaller than 100 nm (69 nm on average) were 0.01, 0.53, and 0.77, respectively. Interestingly, nanoemulsions with droplets smaller than 100 nm showed the highest in vitro bioaccessibility, which could be interpreted as evidence of nanoemulsification enhancing the in vitro bioaccessibility of lycopene.

Physicochemical properties of whey protein, lactoferrin and Tween 20 stabilised nanoemulsions: Effect of temperature, pH and salt

Oil-in-water nanoemulsions were prepared by emulsification and solvent evaporation using whey protein isolate (WPI), lactoferrin and Tween 20 as emulsifiers. Protein-stabilised nanoemulsions showed a decrease in particle size with increasing protein concentration from 0.25% to 1% (w/w) level with Z-average diameter between 70 and 90 nm. However, larger droplets were produced by Tween 20 (120-450 nm) especially at concentration above 0.75% (w/w). The stability of nanoemulsions to temperature (30-90°C), pH (2-10) and ionic strength (0-500 mM NaCl or 0-90 mM CaCl2) was also tested. Tween 20 nanoemulsions were unstable to heat treatment at 90°C for 15 min. WPI-stabilised nanoemulsions exhibited droplet aggregation near the isoelectric point at pH 4.5 and 5 and they were also unstable at salt concentration above 30 mM CaCl2. These results indicated that stable nanoemulsions can be prepared by careful selection of emulsifiers.

Enhanced uptake and transport of (+)-catechin and (-)-epigallocatechin gallate in niosomal formulation by human intestinal Caco-2 cells.

The aim of this study was to evaluate (+)-catechin and (−)-epigallocatechin gallate (EGCG) cellular uptake and transport across human intestinal Caco-2 cell monolayer in both the absence and presence of niosomal carrier in variable conditions. The effect of free drugs and drug-loaded niosomes on the growth of Caco-2 cells was studied. The effects of time, temperature, and concentration on drug cellular uptake in the absence or presence of its niosomal delivery systems were investigated. The intestinal epithelial membrane transport of the drug-loaded niosomes was examined using the monolayer of the human Caco-2 cells. The kinetics of transport, and the effect of temperature, adenosine triphosphate inhibitor, permeability glycoprotein inhibitor, multidrug resistance-associated protein 2 inhibitor, and the absorption enhancer on transport mechanism were investigated. It was found that the uptake of catechin, EGCG, and their niosomes by Caco-2 cells was 1.22±0.16, 0.90±0.14, 3.25±0.37, and 1.92±0.22 μg/mg protein, respectively (n=3). The apparent permeability coefficient values of catechin, EGCG, and their niosomes were 1.68±0.16, 0.88±0.09, 2.39±0.31, and 1.42±0.24 cm/second (n=3) at 37°C, respectively. The transport was temperature- and energy-dependent. The inhibitors of permeability glycoprotein and multidrug resistance-associated protein 2 and the absorption enhancer significantly enhanced the uptake amount. Compared with the free drugs, niosomal formulation significantly enhanced drug absorption. Additionally, drug-loaded niosomes exhibited stronger stability and lower toxicity. These findings showed that the oral absorption of tea flavonoids could be improved by using the novel drug delivery systems.

Optimization of PLGA nanoparticles formulation containing L-DOPA by applying the central composite design

The aim of this work was to prepare L-DOPA loaded poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles by a modified water-in-oil-in-water (W1/O/W2) emulsification solvent evaporation method. A central composite design was applied for optimization of the formulation parameters and for studying the effects of three independent variables: PLGA concentration, polyvinyl alcohol (PVA) concentration and organic solvent removal rate on the particle size and the entrapment efficiency (response variables). Second-order models were obtained to adequately describe the influence of the independent variables on the selected responses. The analysis of variance showed that the three independent variables had significant effects (p < 0.05) on the responses. The experimental results were in perfect accordance with the predictions estimated by the models. Using the desirability approach and overlay contour plots, the optimal preparation area can be highlighted. It was found that the optimum values of the responses could be obtained at higher concentration of PLGA (5%, w/v) and PVA (6%, w/v); and faster organic solvent removal rate (700 rpm). The corresponding particle size was 256.2 nm and the entrapment efficiency was 62.19%. FTIR investigation confirmed that the L-DOPA and PLGA polymer maintained its backbone structure in the fabrication of nanoparticles. The scanning electron microscopic images of nanoparticles showed that all particles had spherical shape with porous outer skin. The results suggested that PLGA nanoparticles might represent a promising formulation for brain delivery of L-DOPA. The preparation of L-DOPA loaded PLGA nanoparticles can be optimized by the central composite design.

Deformable liposomes by reverse-phase evaporation method for an enhanced skin delivery of (+)-catechin

Abstract Background: (+)-catechin, as the most common catechin isomer, is recognized to be an antioxidant which benefits the skin in many ways. The purpose of the present study was to prepare and evaluate a suitable liposomal delivery systems for (+)-catechin topical application. Methods: In this study, catechin-loaded conventional liposomal delivery system, deformable conventional liposomal delivery system and deformable liposomes prepared by reverse-phase evaporation (REV) method were compared. The three systems were characterized for liposome particle size, zeta-potential, entrapment efficiency, drug release, permeability across porcine skin and catechin deposition in the skin. Results: It was revealed that the size of deformable conventional liposomes before freeze-drying and deformable REV liposomes after freeze-drying range from 335.6 ± 71.7 nm to 551.1 ± 53.4 nm, respectively, which were considered to be suitable for skin delivery. The deformable REV liposomes had a higher aqueous volume and thus were able to entrap greater amounts of hydrophilic (+)-catechin (50.0 ± 5.9%) compared to conventional (30.0 ± 3.8%) and deformable conventional liposomes (36.1 ± 4.6%). All liposomal formulations exhibited a prolonged catechin release. Compared to deformable liposomes, the REV deformable liposomes showed a significantly better deposition of (+)-catechin while catechin solution did not permeate into the porcine ear skin. Conclusion: Among all formulations studied, deformable REV liposomes were considered to be favorable for catechin topical delivery.

Oral Delivery of Bovine Lactoferrin Using Pectin- and Chitosan-Modified Liposomes and Solid Lipid Particles: Improvement of Stability of Lactoferrin.

A critical problem associated with delivery of bovine lactoferrin (bLf) by the oral route is low bioavailability, which is derived from the enzymatic degradation in the gastrointestinal tract and poor permeation across the intestinal epitheliums. Particulate carrier systems have been identified to protect bLf against proteolysis via encapsulation. This study aimed to evaluate the physico‐chemical stability of bLf‐loaded liposomes and solid lipid particles (SLPs) modified by pectin and chitosan when exposed to various stress conditions. Transmission electron microscopy results showed liposomes and SLPs had a classic shell‐core structure with polymer layers surrounded on surface, but the structure appeared to be partially broken after digestion in simulated intestinal fluid (SIF). Although HPLC and sodium dodecyl sulphate–polyacrylamide gel electrophoresis methods qualitatively and quantitatively described either liposomes or SLPs could retain intact bLf against proteolysis in SIF to some extent, all liposome formulations showed rapid rate of lipolysis mediated by pancreatic enzymes. On the other hand, all SLP formulations showed higher heat resistance and greater electrolyte tolerance compared to liposome formulations. After 180 days storage time, liposome‐loaded bLf was completely degraded, whereas almost 30% of intact bLf still remained in SLP formulations. Overall, SLPs are considered as primary choice for oral bLf delivery.

Preparation, optimization and characterization of bovine lactoferrin-loaded liposomes and solid lipid particles modified by hydrophilic polymers using factorial design

Bioadhesive liposomes and solid lipid particles (SLPs) modified by pectin and chitosan for oral administration of bovine lactoferrin (bLf) were prepared using a 24 full‐factorial design to identify the key formulation variables influencing particle size and drug entrapment efficiency (EE). Netlike structures of the polymer–particle mixture consisting of a polymeric network in which multiple particles were imbedded were observed by scanning electron microscopy (SEM). Chemical stability of bLf after encapsulation into pectin‐ and chitosan‐modified liposomes and SLPs was confirmed by Fourier transform infrared spectra (FTIR). Bovine lactoferrin was located within phospholipid bilayer, whereas in SLPs bLf was within the matrix. The crystalline nature of bLf after encapsulation was investigated by differential scanning calorimetry (DSC) of drug‐loaded particles, indicating amorphous dispersion of bLf in the polymer–lipid matrix of pectin‐ and chitosan‐modified liposomes and SLPs. In vivo pharmacokinetic investigation of bLf in pectin‐ and chitosan‐modified liposomes and SLPs showed prolonged mean residence time (MRT) of bLf in rat blood and increased the relative bioavailability (Fbio%) by 1.95‐ to 2.69‐fold compared with free bLf. The developed carrier systems are considered to be promising vehicles for oral delivery.

Development of water-in-oil microemulsions with the potential of prolonged release for oral delivery of L-glutathione

Oral delivery of L-L-glutathione is quite a challenge due to the enzymatic and physical barriers in the gastrointestinal tract (GIT). Colloidal delivery systems such as microemulsions (ME) can be valuable for oral delivery of L-glutathione, because they may protect L-glutathione from enzymatic degradation and enhance its permeability across the intestinal epithelium. The aim of this study was to identify ME systems capable of accommodating maximum amounts of L-glutathione in internal aqueous phase intended for oral delivery. Pseudoternary phase diagrams for the systems based on a single or a blend of two oily components, one or two nonionic surfactants and an aqueous phase loaded with L-glutathione were constructed, identified and characterized in terms of morphological, rheological and in vitro release studies. Among the tested formulations, the coarse emulsions resulted in the highest release rate, while the ME and liquid crystal systems provided sustained release of L-glutathione in vitro. There was a linear relationship between the cumulative amount of L-glutathione released from the ME and the liquid crystals, and the square root of time indicting a diffusion controlled process. The release of L-glutathione from the ME and the liquid crystal was related to the concentration of L-glutathione remaining in the formulations. In conclusion, two novel delivery colloidal systems of L-glutathione loaded water-in-oil ME and liquid crystal systems were developed and characterized. In addition, a simple isocratic HPLC analytic method was developed and validated, and was used for the qualitative and quantitative analysis of L-glutathione released from the selected formulations.

Studies of the Rate Constant of l-DOPA Oxidation and Decarboxylation by HPLC

The objective of current investigation was to study the degradation behavior of l-DOPA under different conditions by high performance liquid chromatography (HPLC), and to develop and validate a stability-indicating HPLC method. The developed RP-HPLC method was validated with respect to linearity, accuracy, precision and specificity. Oxidation was found to occur in alkaline and to some extent in thermal conditions, while the drug was stable when incubated at acidic conditions and under photolytic stress. The oxidation of l-DOPA was observed to follow first-order kinetics. The degradation rate constants and half-life were calculated. The cytotoxicity and enzymatic degradation of l-DOPA was examined using the human intestinal epithelial Caco-2 cells. The drug was rapidly decarboxylated by aromatic amino acid decarboxylase to dopamine. The conversion of l-DOPA to dopamine was dose- and time-dependent.